The present invention relates to a method for producing an electrically conductive connection by laser radiation.
The publication xe2x80x9cWelding of Copper with Laser Beamxe2x80x9d in Manufacturing Technology and Measuring Technique 90(1982) 5, pages 239-241 disclose welding of a wire with a copper plate or a copper carrier by means of a laser beam. It has been determined that the materials with high reflection properties and thereby poor absorption are not always weldable and not always weldable with each laser. A good result can be obtained by welding from a blank wire on a copper plate at an angle of 28xc2x0 between the laser beam and a plate. Therefore, the multiple reflection is utilized and the energy of the laser beam is sufficient to release an abnormal absorption and to connect the plate with the wire. In the conducted research the joining partners of the same material, namely copper were utilized.
Accordingly, it is an object of the present invention to provide a method of producing an electrically conductive connection with laser radiation, which avoids the disadvantages of the prior art.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated, in a method of producing an electrically conductive connection with laser radiation, in which the connecting carrier is melted with low melting temperature and the connecting wire is melted with the high melting temperature on the outer surface.
When the method is performed in accordance with the present invention, a mechanical and an electrically conductive connection of an iron wire with a connecting carrier of copper is produced without mechanical force application, or in other words contactlessly by means of a laser beam.
For a joining process no mechanical actions by tools are needed, so that the product, on which the electrically conductive connection is produced, can be designed in a place-saving manner. A joining at the locations which were before unaccessible can be also provided. Furthermore, it has been determined in a surprising manner that by the laser welding no hot cracks in the joint are produced and the fraction of a brittle phase in the joint is very low, so that the permanent strength of the electrical connection is provided.
In accordance with the present invention it is especially advantageous when the laser radiation is performed by a bifocal shot, and the laser radiation is directed to both metal tongues of copper.
In accordance with another feature of the present invention, it is advantageous when the connecting carrier is provided with a corresponding joining part geometry, and moreover the iron wire in the contact region with the connecting carrier is provided with a flattening.